An environmental and economic optimal operation of combined cooling and heating and power generation system for building load

Abstract

This thesis proposes economic and environmental optimal operations of combined heat and power (CHP) systems for two building energy management systems (BEMS). The first BEMS consists of a CHP system, an absorption chiller, an auxiliary boiler, and power grids, but the second BEMS replaces an auxiliary boiler with an electric chiller. The optimal operation problem concerns with multi-objective functions: total operating costs (TOC) and total carbon dioxide emissions (TCOE), while electrical and cooling energy dispatch strategies for each BEMS are used as constraints. The problem can be formulated as a linear program (LP) which can be efficiently solved by LP solvers, such as MATLAB optimization toolbox. This thesis applies BEMS to load demand of a large shopping mall, and the simulation is divided into three parts. The first part designs the capacity of the equipment based on electrical and cooling load profiles of the building to find the most suitable combination for each BEMS. The numerical results demonstrate that the first BEMS can reduce TOC and TCOE by up to 30.2% and 14.0% and the second can decrease TOC and TCOE by up to 37.5% and 21.6%, compared TOC and TCOE of original electricity usage. The second part analyzes optimal operations of BEMS, including the relationship between TOC and TCOE. The analysis results indicate that the relationship between both optimal operations is a trade-off between TOC and TCOE. The final part investigates the risk in the long-term operation of BEMS via the impact of fuel prices on TOC, TCOE, and optimal operations. The assessment results reveal that the fluctuation in fuel prices can cause risks in the long run.